4. Ophioglossum nudicaule Linnaeus, Suppl. Pl. 443. 1781.
Ophioglossum dendroneuron E.P. St.John; O. ellipticum Hooker & Greville; O. mononeuron E.P. St.John
Roots yellowish to pale brown, to 15 per plant, 0.2-0.8mm diam., proliferous at wide intervals. Stem upright, 0.2-1.2 cm, 1-5 mm diam., commonly 2-3 leaves per stem. Trophophore stalk to 0.8 cm, 0.1-0.2 times length of trophophore blade. Trophophore blade spreading, usually plane when alive, green, dull, largest leaves drying with pale central band, ovate to lanceolate, thin, blades less than 0.4 × 0.3 cm in many colonies but blades large, to 4.5 × 1.7 cm in other colonies, herbaceous, base gradually tapered, apex with short apiculum; venation finely complex-reticulate, areoles with only included veinlets in smaller blades but with numerous secondary areoles in largest blades. Sporophores arising at or near ground level, 2-6 times as long as trophophore; sporangial clusters 0.5-1.5cm, 1.5 mm or less wide, mostly with 5-12 pairs of sporangia, apiculum 0.5-1 mm.
Leaves appearing in latter half of winter and early spring, sometimes with second flush in same year after heavy rains. Second-growth fields, vacant lots, roadside ditches, and lawns; 0-90 m; Ala., Ark., Fla., Ga., La., Miss., N.C., Okla., S.C., Tex.; Mexico; West Indies; Central America; South America; Asia; Africa; Pacific Islands.
Ophioglossum nudicaule is much less common than O . crotalophoroides ; they often occur together and are found in the same or similar habitats. The gametophytes of O . nudicaule are typical for the genus (M.R. Mesler et al. 1975). A given colony may be made up of small, medium, or large plants (W.H. Wagner Jr., C. M. Allen, and G.P. Landry 1984).